Pathologic deep margin distance and prognosis in invasive acral melanoma of the sole

BACKGROUND AND OBJECTIVES: The optimal depth of resection margins in melanoma remains unclear. While excessive deep excision may not provide additional oncologic benefit, preservation of plantar subcutaneous fat is important in acral melanoma of the sole. This study evaluated the prognostic significance of pathologically measured deep margin distance. MATERIALS AND METHODS: This multi-institutional retrospective study included patients with invasive sole acral melanoma treated with wide local excision. Deep margin distance was analyzed as a continuous variable using multivariable Cox models (per 1-mm increase). Additional analyses used a prespecified 3-mm cut-off, including Kaplan-Meier, Cox regression, and propensity score matching. RESULTS: A total of 434 patients were included. Deep margin distance was not associated with LRFS (HR 0.99, p = 0.72), DFS (HR 0.97, p = 0.23), or OS (HR 0.99, p = 0.71). No significant differences were observed between groups using the 3-mm cut-off in the overall cohort or after matching. Exploratory analyses with a 2-mm cut-off showed similar results. CONCLUSIONS: Deep margin distance was not associated with survival outcomes in invasive sole acral melanoma. These findings may help guide deep excision planning in conventional wide local excision settings.